Geocachers are smart folks and come up with some brilliant ideas, so I thought I would throw this out to see what you can come up with.

I work in an office with 80-100 people. We have two refridgerators that we keep our lunches in. It seems that there is someone in the office that cannot resist leftover pizza and whenever anyone brings leftover pizza for lunch it disappears before lunchtime. I found this out firsthand yesterday. I asked around, but nobody saw anybody eating my pizza.

My co-workers have come up with a few ideas for dealing with this thief, like putting one of those exploding dye packets from the bank in the bag, but those aren't that easy to get.

My cousin, to catch his wife opening her Christmas gifts early, attached a window alarm sensor inside a gift box, wrapped it, and placed it under the tree with her name on it. The 'screamer' was placed nearby. The gift was opened, of course, and the alarm went off, very loudly.

I would imagine a sturdy cardboard pizza box would work just as well._________________"We never seek things for themselves-what we seek is the very seeking of things"-Pascal

Reminds me of the farmer who was always having his watermelons stolen.

One day, he put up a sign. "One of these watermelons is poisoned."

The next day, he checked the sign. The "One" was scratched out and someone scrawled "Two."

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My suggestion would be to add a special ingredient to the pizza. Not something harmful, but something that would cause him/her to pause before stealing lunch again. I'm thinking a sprinkling of 5-alarm hot sauce, or adding a good deal of salt to the sauce. Obviously this would be meant to only be bait for the thief, not your real lunch. Maybe put it with some brownies made with Ex-lax...

But in reality, most of the places I have worked, stealing (including stealing from fellow employees) was grounds for immediate termination. Stealing someone's lunch isn't worth risking their job (unless it's a really lousy job). So perhaps the best deterrent might be a sign that says:

The ink is the right idea, just not the exploding part though. Lift the cheese and put a bunch of colored dye on the pizza, then replace the cheese. Put that one piece of pizza on top (if there are many). It's very possible that the culprit will eat the pizza and not even know that his teeth are now very stained (temporarily) blue or red or orange (blue looks funniest)! You'll find your thief, and he will be so embarrassed that he will not do that again. Just don't forget though and eat it yourself!

And to be more precise, make the dye "small drops" so that if he/she bites and looks at the pizza, hopefully the dye drops will either be taken in completely with the bite.

By the way, this is an awesome fun prank to do to friends or family just for fun as well. _________________"There is a pleasure in the pathless woods..." - Lord Byron